Deploying reconfigurable intelligent surface (RIS) to enhance wireless transmission is a promising approach. In this paper, we investigate large-scale multi-RIS-assisted multi-cell systems, where multiple RISs are deployed in each cell. Different from the full-buffer scenario, the mutual interference in our system is not known a priori, and for this reason we apply the load coupling model to analyze this system. The objective is to minimize the total resource consumption subject to user demand requirement by optimizing the reflection coefficients in the cells. The cells are highly coupled and the overall problem is non-convex. To tackle this, we first investigate the single-cell case with given interference, and propose a low-complexity algorithm based on the Majorization-Minimization method to obtain a locally optimal solution. Then, we embed this algorithm into an algorithmic framework for the overall multi-cell problem, and prove its feasibility and convergence to a solution that is at least locally optimal. Simulation results demonstrate the benefit of RIS in time-frequency resource utilization in the multi-cell system.
翻译:部署可调整的智能表面(RIS)以加强无线传输是一个很有希望的方法。 在本文中,我们调查了大型多RIS辅助多细胞系统,每个细胞都安装了多个RIS。与全面缓冲方案不同,我们的系统中的相互干扰并不先验,因此我们应用负载组合模型来分析这个系统。目标是通过优化细胞的反射系数,最大限度地减少用户需求所需的总资源消耗量。细胞高度结合,总的问题是非凝固。要解决这个问题,我们首先调查单个细胞的干扰情况,并提议一种基于多数化-最小化方法的低兼容性算法,以获得当地最佳解决办法。然后,我们将这一算法纳入一个总体多细胞问题的算法框架,证明它的可行性和趋同至少是当地最佳的解决办法。模拟结果显示,在多细胞系统中的时间频度资源利用方面,RIS的好处。